Kepler-206 d
Astrophysical Synthesis & Habitability Characterization
Kepler-206 d is a confirmed terrestrial exoplanet orbiting the star Kepler-206, located approximately 1938.8 light-years (594.45 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0085% across the stellar disk), this world measures 1.19 Earth radii and has a measured mass of 1.81 Earth masses. Combining its mass and radius yields a mean bulk density of 5.92 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.28 g⊕ (12.55 m/s²), and an escape velocity of 13.8 km/s.
In its orbital architecture around Kepler-206, Kepler-206 d completes one full revolution every 23.443 Earth days at a semi-major axis of 0.163 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 75.6 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 681 K (+408°C / +766°F) and receiving 44.17 S⊕ (~60,115 W/m²), Kepler-206 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-206 is classified as a stellar host with an effective photospheric temperature of 5,764 K, a radius of 1.185 R☉, a mass of 0.957 M☉, an estimated bolometric luminosity of 1.391 L☉. Stellar evolution modeling indicates an estimated stellar age of 8.32 Gyr and a metallicity of [Fe/H] = 0.021 dex (near-solar heavy-element abundance). From Earth, Kepler-206 shines at apparent V-band magnitude 13.507 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-206 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-206 d sharing its stellar neighborhood alongside Kepler-206 b, Kepler-206 c.
Methodology: Computed using the Schulze-Makuch et al. (2011) weighted metric comparing physical interior (radius, estimated density) and surface thermal regime (escape velocity, equilibrium temperature).
Discovery Facility: Kepler · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | Kepler-206 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,764 K |
| Stellar Radius | 1.1850 R☉ |
| Stellar Mass | 0.9570 M☉ |
| Bolometric Luminosity | 1.391 L☉ |
| Metallicity [Fe/H] | 0.021 dex |
| Stellar Age | 8.320 Gyr |
| Apparent Magnitude | V: 13.507 · G: 13.461 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.163000 AU |
| Orbital Period | 23.443 days |
| Mean Orbital Velocity | 75.6 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 85.8300° |
| Mean Bulk Density | 5.92 g/cm³ (13.8 km/s vesc) |
| Insolation Flux | 44.1700 S⊕ (~60,115 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1938.800 LY (594.447 pc) |